Get out and measure your ingredients.
Preheat oven to 350ºF.
Prepare three 8-inch round cake pans by spraying them with cooking spray and coating them with a fine layer of flour. Set aside.
In a large mixing bowl, combine brown sugar, eggs, and butter with a hand mixer.
Add cocoa powder. Slowly add boiling water while mixing. Blend until smooth.
Add flour and baking soda. Beat again until smooth.
Add sour cream. Beat again until smooth.
Divide batter between the three prepared cake pans.
Bake for 15 minutes or until toothpick comes out clean.
Allow cakes to cool for 15 minutes before flipping them out onto your work surface. It may help to run a knife around the edges to release the cake.
Allow cakes to cool completely before frosting.